1. Field of the Invention
This invention relates to electrical connectors suitable for use with high frequency and radio frequency signals.
2. Description of the Prior Art
A wide variety of connectors are known in the prior art. In many applications, a single structure, such as a plug housing, must contain a large number of connecting means in order to allow many signal paths to be connected through a single plug. With an increasing number of connectors contained on a single plug device, the insertion and removal force required when connecting and disconnecting the plugs increases, often times to an unacceptable level. To circumvent this problem, the so-called "zero insertion force" connectors are used in certain applications. For example, Fairchild Camera & Instrument Corporation, the assignee of this invention, manufactures and sells "pinless contact rings" under their part numbers 95-8349-01 (24 pins) and 95-8349-00 (60 pins) for use with their Sentry.RTM. series of test systems. Such pinless contact rings typically comprise a ring of insulating material such as a suitable plastic material into which a plurality of holes have been formed. Into each of these holes is placed a malleable conductive material which is held securely in its associated hole within the pinless contact ring, and which extends on either side of the pinless contact ring in order to allow electrical connection to each side. Thus, the pinless contact rings may be placed on a first printed circuit board with each of the conductive segments contacting a desired electrical connection on the first printed circuit board. Thereafter, a second printed circuit board is placed on top of the pinless contact ring, with the conductive members of the pinless contact ring making electrical contact with various portions of the second printed circuit board. In this manner, electrical connection is established between the first and second printed circuit boards, without requiring any insertion or removal force associated with other prior art plug means.
However, such pinless contact rings are not suitable for use with high frequency and radio frequency signals because the characteristic impedance of the through conductors placed in the pinless contact ring is not controlled. Furthermore, because the pinless contact ring is necessarily made of a non-conductive material, shielding between adjacent conductive members is virtually non-existent, with cross-talk between conductive members the result.
Another attempt to make a zero insertion force connector for providing connection to an integrated circuit device is described in U.S. Pat. No. 4,150,420 issued Apr. 17, 1979 to Berg. The Berg structure provides a plurality of electrical connectors by the use of an equal plurality of metal "fingers", which are biased by a resiliant material such as silicone rubber. However, the Berg structure does not provide coaxial connectors.
In order to provide adequate shielding and a controlled characteristic impedance, coaxial cable is used. In order to maintain this shileding and characteristic impedance at the connection point, coaxial connectors are used. Such coaxial connectors, including the standard "BNC" type connectors, are well known in the prior art. However, when a large number of coaxial connections must be made, a correspondingly large number of coaxial connectors must be used. This results in rather high cost, and a large amount of effort to connect and disconnect the large number of coaxial connectors, as well as to maintain the proper connections among coaxial cables.
One solution to this problem of providing a number of coaxial connections is to form a number of coaxial connectors in a single connector block. Multiple coaxial connectors within a single block are described, for example, in the MULTIPLE COAXICON CONNECTORS catalog number 74-286 available from AMP Incorporated, Harrisburg, Pa. However, such multiple coaxial connectors require a large insertion force and a large removal force, as well as being rather expensive, bulky, and awkward to handle.
Furthermore, in many applications, the shear bulk of such prior art coaxial connectors is prohibitive. For example, in electronic component testing and more particularly advanced semiconductor device testing, a large number of connections must be made to a semiconductor device in order to test the device. Furthermore, in semiconductor testing, such connections must be made at the wafer level prior to packaging, for example, in the dual in line packages (DIPs) or the newer "leadless" packages (also called "chip carriers"). Because of the limited space available on the circuit boards which must be placed on the test systems in order to test either wafers or packaged devices, as well as the sometimes frequent changing of test boards required in the semiconductor industry, such prior art coaxial connectors are at best undesirable, and at worst impossible to use given the limited amount of space available.